Hadamard's maximum determinant problem asks to find the largest possible determinant (in absolute value) for any matrix whose elements are taken from some set. Hadamard
(1893) proved that the determinant of any complex
matrix
with entries in the closed unit disk
satisfies
|
(1)
|
with equality attained by the Vandermonde matrix of the roots of unity (Faddeev and
Sominskii 1965, p. 331; Brenner and Cummings 1972). The first few values for
for
,
2, ... are 1, 2,
, 16,
, 216, ..., and the squares of these are 1, 4, 27,
256, 3125, ... (OEIS A000312).
A (-1,1)-matrix attaining the bound is known as a Hadamard
matrix (Brenner and Cummings 1972). The same bound applies to all (-1,1)-matrices,
and sharper bounds are known for orders
that are not a multiple of 4. A summary of what is known
about such bounds is given by Orrick and Solomon.
For a (0,1)-matrix, Hadamard's bound can be improved to
|
(2)
|
(Faddeev and Sominskii 1965, problem 523; Brenner and Cummings 1972).
For an (0,1)-matrix (i.e., a
binary matrix), the largest possible determinants
for
, 2, ... are 1, 1, 2, 3, 5, 9, 32, 56, 144, 320, 1458, 3645,
9477, ... (OEIS A003432). The numbers of distinct
binary matrices having the largest positive determinant are 1, 3, 3, 60, 3600, 529200,
75600, 195955200, 13716864000, ... (OEIS A051752).
| matrices | |
| 1 | |
| 2 | |
| 3 |
For an (-1,1)-matrix, the largest
possible determinants
for
, 2, ... are 1, 2, 4, 16, 48, 160, ... (OEIS A003433;
Ehlich and Zeller 1962, Ehlich 1964). The numbers of distinct
-matrices having the largest positive determinant are
1, 4, 96, 384, 30720, ... (OEIS A188895, indexed
there by
).
is related to the largest possible
-matrix determinant
by
|
(3)
|
for (Williamson 1946, Brenner and Cummings 1972).
| matrices | |
| 1 | |
| 2 |
For an (-1,0,1)-matrix, the
largest possible determinants
are the same as
(Ehlich 1964, Brenner 1972). The numbers of
-matrices having maximum positive determinants are 1,
4, 240, 384, 30720, ... (OEIS A051753).
For order 198, Georgiou and Stylianou (2026) attained the Ehlich-Wojtas bound by constructing a D-optimal matrix. Thus the largest
absolute determinant of a (-1,1)-matrix
of that order is .